A performance training apparatus which has the navigation function of guiding a performer's performance is known conventionally. For example, in an electronic keyboard instrument having the navigation function, light emitting elements such as light emitting diodes are provided in correspondence to the keys of a keyboard. As the performance of a pre-stored melody progresses, the performer is caused to recognize a key to be depressed and a timing of depressing the key by causing a light emitting element for the key to emit light. When the performer does not depress the key even when the timing of depressing the key has come, the performance of the melody is stopped to thereby synchronize the performer's performance with the progress of performance of the melody.
When the key is depressed before the key depression timing comes, however, no appropriate measures cannot be taken properly, and a musical sound based on the depression of the key is produced. However, production of this musical sound cannot be synchronized with production of a musical sound of another part such as an accompaniment sound contained in the melody data. Some other conventional apparatus are arranged such that when a key is depressed before a proper timing at which the key is to be depressed, a musical sound is not produced at that timing, and that when the proper timing has come, the musical sound is produced. Since no musical sound is produced when the key is depressed, however, the performer will greatly feel that something is wrong.